Hello,
If I have two steady state scenarios with identical boundary conditions (suction and discharge tank hydraulic grade lines), shouldn't the static lift for the pump be similar under both scenarios? The only difference in the two scenarios is the addition of a nodal demand to simulate a fire flow test. I am definitely misunderstanding something here...
Regards,
Youssef
If the fire flow is between the pump and the tank, then the HGL drops.
Hi Tom,
Great insight, thank you!
So then in that case, with the additional nodal fire flow demand, is it the correct understanding that WaterGEMS calculates the static lift across a pump based on the immediate upstream (suction) and downstream (discharge) junctions and not based on the static hydraulic grade lines between the suction and discharge tanks? I hope you can clarify my misunderstanding.
When you say that WaterGEMS calculates the "static lift", are you referring to the zero flow point on the system head curve? If so, that point shows the head difference between the upstream and downstream side of the pump with zero flow forced through it. The downstream demands and other conditions are still used so if there is a downstream demand (and another source like a downstream tank that supplies it), then the downstream HGL will be impacted by this because the downstream tank will supply the demands, dropping the HGL on the pump discharge side as Tom mentioned.
See more about how system head curves work in the following article (I added a note to it about this subject): Understanding System Head Curves in WaterGEMS, WaterCAD, and SewerCAD
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Answer Verified By: Sushma Choure
Excellent tips, what you and Tom mentioned exactly clarified my misunderstanding with what was happening. Thank you so much Jesse and Tom!